Optic neuritis is an inflammation of the optic nerve, the bundle of nerve fibers that transmits visual information from your eye to your brain. Pain and temporary vision loss are common symptoms of optic neuritis.

Optic neuritis is highly associated with multiple sclerosis, a disease that causes inflammation and damage to nerves in your brain and spinal cord. In some people, signs and symptoms of optic neuritis may be the first indication of multiple sclerosis.

Most people who have a single episode of optic neuritis eventually recover their vision. Treatment with steroid medications may speed up vision recovery after optic neuritis.

Optic neuritis usually affects one eye. Symptoms might include:

Pain. Most people who develop optic neuritis experience eye pain that's worsened by eye movement. Sometimes the pain feels like a dull ache behind the eye.

Vision loss. Most people experience at least some temporary reduction in vision, but the extent of vision loss varies. Noticeable vision loss usually develops over hours or days. Exercise or a hot bath or shower may exaggerate the vision loss. Vision loss is permanent in some cases.

Loss of color vision. Optic neuritis often affects color perception. You might notice that colors appear less vivid than normal.

Flashing lights. Some people with optic neuritis report seeing flashing or flickering lights.

When to see a doctor

Eye conditions can be serious. Some can lead to permanent vision loss, and some are associated with other serious medical problems. Contact your doctor if:

You develop new symptoms, such as eye pain or a change in your vision.

Your symptoms worsen or don't improve with treatment.

You have unusual symptoms, including numbness or weakness in one or more limbs, which may be an indication of a neurological disorder.

The exact cause of optic neuritis is unknown. However, optic neuritis is believed to develop when the immune system mistakenly targets the substance covering your optic nerve (myelin), resulting in inflammation and damage to the myelin.

The following autoimmune conditions often are associated with optic neuritis:

Multiple sclerosis. Multiple sclerosis is a disease in which your autoimmune system attacks the myelin sheath covering nerve fibers in your brain and spinal cord. In people with optic neuritis, the risk of developing multiple sclerosis following one episode of optic neuritis is about 50 percent over a lifetime.

Your risk of developing multiple sclerosis after optical neuritis increases further if an MRI scan shows lesions on your brain.

Neuromyelitis optica. In this condition, inflammation occurs in the optic nerve and spinal cord. Neuromyelitis optica has similarities to multiple sclerosis, but neuromyelitis optica doesn't cause damage to the nerves in the brain as often as multiple sclerosis does. Optic neuritis arising from neuromyelitis optica tends to be more severe than optic neuritis associated with multiple sclerosis.

Other autoimmune conditions, such as sarcoidosis and systemic lupus erythematosus, have also been associated with optic neuritis.

Other factors that have been linked to the development of optic neuritis include:

Infections. Bacterial infections, including Lyme disease, cat-scratch fever and syphilis, or viruses such as measles, mumps and herpes can cause optic neuritis.

Drugs. Some drugs have been associated with the development of optic neuritis. One of these drugs is ethambutol (Myambutol), which is used to treat tuberculosis.

Optic nerve damage. Most people have some permanent optic nerve damage following an episode of optic neuritis, but the damage might not cause symptoms.

Decreased visual acuity. Most people regain normal or near normal vision within several months. However, a partial loss of color discrimination may persist. For some people, vision loss may persist after the optic neuritis has improved.

Side effects of treatment. Steroid medications used to treat optic neuritis subdue your immune system, which causes your body to become more susceptible to infections. Long-term use of steroids may also cause other conditions such as thinning of your bones (osteoporosis).

If you have signs and symptoms of optic neuritis, you'll likely see your family doctor or a general practitioner. However, you might be referred immediately to a doctor who specializes in diagnosing and treating eye diseases (ophthalmologist).

Here's some information to help you prepare for your appointment and know what to expect from your doctor.

What you can do

Write down any symptoms you're experiencing, and for how long. Describe your symptoms as specifically as possible, including rating the severity of your vision loss and whether you see colors differently.

Write down key personal information, including any recent stressors or major life changes.

Make a list of your key medical information. Your doctor will want to know about any recent infectious illnesses you've had, as well as any other conditions with which you've been diagnosed. Also write down the names of all prescription and over-the-counter medications and supplements you're taking.

Take a family member or friend along. Someone who accompanies you can help you remember information your doctor gives you.

Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. For optic neuritis, questions to ask your doctor include:

What is likely causing my symptoms?

Are there other possible causes?

What tests do I need?

What treatments do you recommend?

What are the possible side effects of the medications you're recommending?

How fully do you expect I will recover, and how long will that take?

How will you monitor my progress?

Does this condition put me at risk of other medical conditions?

How will you evaluate my risk of related conditions?

If tests indicate that I'm at increased risk of other medical conditions, are there treatments that can help reduce my risk?

Are genetic factors associated with my condition? Are my relatives at risk?

Do you recommend genetic testing for my immediate family?

I have other health conditions. How can I best manage these conditions together?

Do you have brochures or other printed material I can take with me? What websites do you recommend?

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

When did you begin experiencing symptoms?

How would you describe your symptoms?

How significantly has your vision decreased?

Do colors look less vivid?

Have your symptoms changed over time?

Does anything seem to make your symptoms better, or worse, such as strenuous exercise or a hot shower?

Have you noticed problems with movement and coordination?

Have you noticed numbness or weakness in your arms or legs?

Have you recently had an infection?

Have you been diagnosed for other medical conditions?

Have any close relatives been diagnosed with optic neuritis?

Have any close relatives been diagnosed with multiple sclerosis?

You're likely to see an ophthalmologist for a diagnosis, which is generally based on your medical history and an exam. The ophthalmologist likely will perform the following eye tests:

Ophthalmoscopy. During this examination, your doctor shines a bright light into your eye and examines the structures at the back of your eye. This eye test evaluates the optic disk, where the optic nerve enters the retina in your eye. The optic disk becomes swollen in about one-third of people with optic neuritis.

Pupillary light reaction test. Your doctor may move a flashlight in front of your eyes to see how your pupils respond when they're exposed to bright light. Pupils in eyes affected by optic neuritis don't constrict as much as those in healthy eyes do when stimulated by light.

Other tests to diagnose optic neuritis may include:

Visual evoked response. During this test, you sit before a screen on which an alternating checkerboard pattern is displayed. Attached to your head are wires with small patches to record your brain's responses to the visual stimuli. This type of test detects the slowing of electrical conduction resulting from damage to the optic nerve.

Magnetic resonance imaging (MRI) scan. An MRI scan uses a magnetic field and pulses of radio wave energy to make pictures of your body. During an MRI to check for optic neuritis, you may be injected with a contrast solution to make the optic nerve and other parts of your brain more visible on the images.

An MRI is important to determine whether there are damaged areas (lesions) in your brain, which indicate a high risk of developing multiple sclerosis. An MRI can also rule out other causes of visual loss, such as a tumor.

Blood tests. A blood test is available to check for antibodies for neuromyelitis optica. People with severe optic neuritis may undergo this test to determine whether they're likely to develop neuromyelitis optica.

Optic neuritis usually gets better on its own. In some cases, steroid medications are used to reduce inflammation in the optic nerve. Possible side effects from steroid treatment include weight gain, mood changes, stomach upset and insomnia.

Steroid treatment is usually given by vein (intravenously). Intravenous steroid therapy may speed vision recovery, but it doesn't appear to affect the extent to which you'll recover vision you've lost. Steroid treatment is also used to reduce the risk of developing multiple sclerosis or slow its development.

When steroid therapy fails and severe vision loss persists, a treatment called plasma exchange therapy may help some people recover their vision. However, studies haven't confirmed that plasma exchange therapy is effective for optic neuritis.

Preventing multiple sclerosis

If you have optic neuritis, and you have two or more brain lesions evident on MRI scans, you might benefit from drugs that help prevent multiple sclerosis. These injectable drugs, including interferon beta-1a (Avonex, Rebif) and interferon beta-1b (Betaseron, Extavia), are used to prevent or delay the development of multiple sclerosis in people at high risk of the disease.

Prognosis

Most people regain close to normal vision within 12 months after an optic neuritis episode.

People with multiple sclerosis or neuromyelitis optica might have a greater risk of recurrent attacks of optic neuritis. Optic neuritis can recur in people without underlying conditions, but those people generally have a better long-term prognosis for their vision than do people with multiple sclerosis or neuromyelitis optica.

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